This little cygnet (baby swan) is also the latch that opens the top of the iron to reveal the slug.
Patent Models are very collectible and rare. To learn more about the history of Patent Models in the United States, and about the destruction suffered after two fires in the US Patent Office, see the following article by Donald W. Hogan. Unwanted Treasures of the Patent Office. American Heritage Magazine, Volume 9, Issue 2, February 1958.